Solid state fermentation of broiler litter for production of biocontrol agents

Abstract

Several varieties of heat-sterilized broiler litter with 60% (wet basis, wb) moisture content were substrate in solid-state fermentations to produce biocontrol agents. Litter varieties included litter produced by one flock of broilers from medicated and non-medicated controlled rations, and litter produced by two flocks and four flocks on a single application of bedding material from medicated commercial sources. Litter preparations were inoculated with monocultures of Bacillus thuringiensis serovar japonensis strain Buibui, a pathogen of Japanese beetle larvae ( Popillia japonica), or Pseudomonas fluorescens 2-79. B. thuringiensis did not grow in unextracted 1-flock litter nor in water extracted litter, but grew in methanol extracted litter to 5×10 10 cell forming units (CFU)/g litter (dry weight, dw) and a spore count of 1×10 10 CFU/ g litter (dw). B. thuringiensis also grew in unprocessed 2-flock and 4-flock litter, achieving cell counts of 3×10 9 and 1×10 9 CFU/ g litter (dw), respectively, and spore counts of 1×10 9 CFU/ g litter (dw). P. fluorescens grew in medicated 1-flock litter with no extraction to a cell density greater than 4×10 11 CFU/ g litter (dw). Bioassays in soil containing over 0.5% (db) litter fermented with B. thuringiensis resulted in over 90% mortality in 21 days for first instars of Japanese beetle when compared to a control treatment using compost without fermented litter. The investigations demonstrate that bacterial biocontrol agents produced via solid substrate fermentations using broiler poultry litter have potential in biocontrol applications in the soil environment.